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I had water infiltrate my right headlamp area (645Ci). Light went out and of course headlamp error on. Diagnosis confirms:

Bulb OK (switched sides)
Igniter OK (switched sides)
High beam OK (hi-beam comes on when I manually pull lever)
Halo OK
I was told it was the ballast (control assy). Got some great info from the forum and removed the bumper and headlight assembly (relatively easy). Now all I have to do is replace the controller (PN# 1 307 329 074). I just want to make sure it is in fact the controller that is bad.

BEFORE I BUY THE CONTROLLER AND REPLACE IT IS THERE A WAY TO CONFIRM IT IS BAD?